1. Field of the Invention
This invention relates generally to a gyro apparatus (angular velocity detecting apparatus) and, more particularly, is directed to a gyro apparatus employing a tuning fork.
2. Description of the Prior Art
An example of a prior art tuning fork-type gyro apparatus will be described first with reference to FIG. 1. FIG. 1 is a perspective view of such a prior art tuning fork-type gyro apparatus. In this tuning fork-type gyro apparatus shown in FIG. 1, a tuning fork 1 is attached to a base table 2 through a flexible shaft 3. To the tuning fork 1 at its positions near the upper end thereof, there are mounted displacement detectors 6 and drive windings 4 respectively, and the outputs from the displacement detectors 6 are supplied together through a drive amplifier 5 to the drive windings 4 whereby to keep the vibration amplitude of the tuning fork 1 constant. If an angular velocity .OMEGA. is applied around the axis of the flexible shaft 3 of the tuning fork 1, that is, an input axis or a tuning fork axis Z--Z, there are respectively generated Coriolis forces Fc which correspond to a vibration speed v of the tuning fork 1 and the input angular velocity .OMEGA. and which Coriolis forces Fc are parallel to each other but opposite in direction. By the Coriolis forces Fc, the whole of the tuning fork 1 is rotated around the input axis Z--Z in an AC fashion. In other words, a twisting vibration is generated in the tuning fork 1.
In the prior art example shown in FIG. 1, the twisting vibration of the tuning fork 1 is detected by a twising detector 8 mounted on the base portion of the tuning fork 1 and the detected output from the detector 8 and the output from the drive amplifier 5 are synchronously rectified by a demodulator 7 to thereby detect the input angular velocity .OMEGA., thus a gyro apparatus being constructed.
However, according to such a prior art tuning fork-type (or vibration-type) gyro apparatus, the heavy-weighted tuning fork 1 is supported in a cantilever fashion so that the load capacity of the flexible shaft 3 must be made sufficiently large. This causes the flexible shaft portion 3 to become large in size. Further, since the Coriolis force Fc corresponding to the input angular velocity .OMEGA. is derived as a rotation angle of the tuning fork 1 having a large moment of inertia, the sensitivity for the input angular velocity .OMEGA. is low. If this sensitivity is increased, the whole of the gyro apparatus becomes large in size. Furthermore, since the flexible shaft 3 and the twisting detector 8 are formed of separate members, there are problems, for example, that the construction of the gyro apparatus becomes complicated, also the detection sensitivity for the input angular velocity .OMEGA. is low and so on.